Fuel sprayback inhibitor for two cycle engines

ABSTRACT

D R A W I N G A FUEL SPRAYBACK INHIBITOR FOR USE WITH THE CARBURETOR OF A TWO CYCLE INTERNAL COMBUSTION ENGINE COMPRISING AN AIR INTAKE DUCT HAVING WALLS DEFINING A LONGITUDINALLY EXTENDING AIR PASSAGE TERMINATING AT ONE END IN AN INLET AND TERMINATING AT THE OTHER END IN AN OUTLET COMMUNICATING WITH THE INTAKE OF THE CARBURETOR, THE AIR PASSAGE EXTENDING VERTICALLY AND NORMAL TO THE CARBURETOR INTAKE.

United States Patent [1 1 Keenan et al.

[ 1 FUEL SPRAYBACK INHIBITOR FOR TWO CYCLE ENGINES [75] Inventors: Daniel J. Keenan, Merrill; Norman F. Welzein, Saginaw, both of Mich.

[73] Assignee: Samuel C. Adams, Reese, Mich.,

by said Welzein [22] Filed: Sept. 23, 1970 [21] Appl. No.: 74,543

[52] US. Cl. 123/73 A, 123/74 A, 123/119 R, 123/119 CG, 123/142, 55/DIG. 28, 55/276, 261/1 [51] Int. Cl.. F02b 33/04, F02b 33/12, F02m 17/00 [58] Field of Search. 123/142, 73 A, 73 AA, 119 R, 123/73 R, 119 CG, 74 R, 74 A; 55/DIG. 28,

[56] References Cited UNITED STATES PATENTS 2,153,069 4/1939 Barr et a1 55/DIG. 28 2,175,106 10/1939 Burns 123/119 CG 2,267,706 12/1941 Baile 2,963,111 12/1960 'Rohrbacher 55/276 3,382,853 5/1968 Kinoshita 123/73 R 3,486,490 12/1969 Paron 123/74 R 900,083 10/1908 Clark 123/73 A 1,619,894 3/1927 Swartz 123/73 A OTHER PUBLICATIONS 1950 Buick Shop Manual, Page 69, FIG. 3-] on page 69 and subparagraph d thereon Primary Examiner-Wendell E. Burns Attorney, Agent, or Firm-Learman & McCulloch 5 7] ABSTRACT A fuel sprayback inhibitor for use with the carburetor of a two cycle internal combustion engine comprising an air intake duct having walls defining a longitudinally extending air passage terminating at one end in an inlet and terminating at the other end in an outlet communicating with the intake of the carburetor, the

air passage extending vertically and normal to the carburetor intake. 1

12 Claims, 3 Drawing Figures UL Mae 111,411.

FIGB

L INVENTOR ATTORNEYS FUEL SPRAYBACK INHIBITOR FOR TWO CYCLE ENGINES FIELD OF THE INVENTION This invention relates to an air intake device for an internal combustion engine and more particularly to an air intake device especially adapted to inhibit fuel sprayback normally associated with two cycle engines.

BACKGROUND OF THE INVENTION Two cycle engines are commonly used on lightweight vehicles such as snowmobiles, motor bikes, watercraft, and hand-held apparatus such as chain saws. Because the well known float type carburetors present fuel mixture enrichment problems on some two cycle internal combustion engine installations, the commercially available diaphragm carburetor has received wide acceptance. In two cycle engines, the air-fuel mixture flows from the carburetor into the crankcase through the cylinder intake ports as a result of sub-atmospheric pressure being produced in the engine crankcase. As the engine operates, and the piston moves through its power stroke to compress the fuel mixture in the crankcase, the resulting compression causes a reversal of the fuel mixture flow and expells a certain amount of the carbureted air through the same passage by which the carbureted air is drawn into the crankcase. This condition is described as fuel sprayback.

The fuel used in two cycle engines generally comprises a gasoline and oil mixture. The fuel sprayback is hazardous because of the high combustibility of gasoline. Moreover, when the gasoline portion of the mixture evaporates, a film of oil remains on the sprayed object, thereby rendering the object unusable or requiring a costly cleaning operation. The discharge of the fuel mixture is also a substantial waste of otherwise useable fuel.

Since energy producing gasoline is lost in the sprayback, the power output of two cycle internal combustion engines has been substantially reduced. Because the sprayback also includes oil, there may be insufficient oil in the combustion chamber during the power portion of the cycle to properly lubricate and cool the engine. Thus, the operating temperatures of conventional two cycle, internal combustion engines have been excessively high.

The construction of some two cycle engines include Reed valves which comprise a door on the air intake opening that opens in response to sub-atmospheric pressure in the crankcase and closes when the pressure rises as the volume of the combusion chamber decreases. Such valves are subject to wear and the maintenance and replacement of such valves is expensive.

Accordingly, it is a prime object of the present invention to eliminate or greatly minimize fuel sprayback from a two cycle internal combustion engine.

It is another object of the present invention to provide carburetor air intake device which will reduce the operating temperatures of two cycle internal combustion engines.

Still another object of the present invention is to provide an air-intake device which will minimize the fuel consumption of the two cycle internal combustion engine.

Yet another object of the present invention is to provide an air intake device which will increase the power output of a two cycle internal combustion engine.

A further object of the present invention is to provide an air intake device which will minimize the hazards of operating a two cycle internal combustion engine.

A still further object of the present invention is to provide an air intake device for use with the carburetor of a two cycle engine which will limit the fuel sprayback, particularly in the low speed range.

Another object of the present invention is to eliminate the necessity for a Reed valve in an engine while retaining the function of the valve.

Other objects and advantages of the present invention will become apparent to those skilled in the art from the following description.

SUMMARY OF THE INVENTION An air intake device for the carburetor of a two cycle internal combustion engine and comprising a duct having walls defining an upright air passage terminating at its upper end in an inlet and terminating at its lower end in a horizontal outlet in fluid communication with the air intake of the carburetor. The height of the air passage and the spacing of the duct wall opposite the carburetor intake are so selected as to inhibit the discharge of fuel sprayback emitted by the carburetor.

The present invention more readily may be understood by reference to the accompanying drawings in which:

FIG. 1 is a vertical sectional view illustrating an air intake device constructed according to the invention and mounted on the carburetor of a two cycle engine;

FIG. 2 is a front elevational view illustrating the air intake device only; and

FIG. 3 is a sectional view of the air intake device only and taken along the line 3--3 of FIG. 2.

Apparatus constructed according to the invention is particularly adapted for use with a two cycle internal combustion engine, schematically illustrated at E, such as the 297 cubic centimeter engine, Type AB19 or AB21, manufactured by FICHEL-SACl-IS, Schweinfurt, Germany. The engine E includes an engine block 1 1, having a cylinder 16 and a piston 14 which cooperates to define a variable volume combustion chamber 12 above the piston and a variable volume working chamber 12a below the piston. The block 11 includes the usual fuel-air mixture inlet port 10 in the side wall thereof in communication with the cylinder 16. An exhaust port 11a is also provided in the cylinder side wall slightly above the inlet port 10 to exhaust the products of combustion at the end of the stroke and is connected with an exhaust manifold (not shown). Fuel injection ports 14a are provided on the cylinder side wall and communicate with the engine crankcase via ducts (not shown) in the engine block E. The piston 14 is connected to a crank (not shown) rotatably mounted in the engine crankcase and reciprocates in the cylinder 16 to open and close the inlet port 10 in the usual manner.

A spark plug 13, of conventional construction, is

threaded in the block 11 and includes a spark electrode 13a disposed in the combustion chamber 12 for igniting the fuel in the conventional manner. The spark plug 13 is connected to a spark distributor as usual.

Mounted on the engine E in communication with the opening 10 is a diaphragm operated carburetor C, such as type HD or HR, manufactured by TillotsonCarburetor Company of Toledo, Ohio.

The carburetor C includes a housing H having a fuelair mixture discharge port 18 in one side wall 19 and an air inlet port 20 having an axis 20 in an opposite side wall 21. The carburetor C is connected by a conduit 23 to a suitable source 22 of fuel which, for two cycle engines, conventionally comprises a gasoline and oil mixture. As the piston 14 moves to the chain line position shown in FIG. 1 to compress the chamber 12 and close the fuel injection ports 14a and exhaust port 11a, air is drawn through the port 20 to be mixed with fuel from the source 22 in the usual manner and the fuel-air mixture, as illustrated by the arrow a, passes into the working chamber 12a below the piston 14 (in the chain line position shown in FIG. 1) as the pressure in the engine crankcase is reduced to less than that of the atmosphere. As the piston 14 moves toward the solid line position illustrated in F IG. 1, the fuel passes under pressure, from the working chamber 12a to the crankcase and when the piston 14 reaches the solid line position to expose the injection ports 14a, the fuel passes from the crankcase into the combustion chamber 12 in the direction indicated by the arrows x.

On the power stroke of the piston 14, the fuel in the crankcase is pressurized and a portion of the fuel-air mixture is driven outwardly through the port 18 and the air inlet port 20 in the direction of the arrow c. This exhausting of a portion of the previously carbureted fuel and air is referred to as fuel sprayback.

To inhibit fuel sprayback and the loss of the fuel, a tuned air-intake device or fuel sprayback inhibitor, shown generally at A, is provided and comprises a fantail shaped duct including spaced, parallel, opposed side walls 24 and 26, respectively, joined by upwardly diverging side walls 28 to define a vertically extending passage P having an inlet opening 32 at its upper end for admitting air. At the lower end of the front wall 24 is an outlet opening 25 around which is a mounting flange 36 having suitable apertures 37 for bolts 38 threaded into the carburetor C. The area of the inlet 32 of the duct A is slightly larger than the outlet 25 of the duct A so that a unit of air entering the opening 32 is accelerated as it passes through the passage P to the discharge opening 25, thereby more rapidly returning the fuel entrained in the air stream to the carburetor. portion The side walls 28 of the duct A merge into a curvilinear end wall portion 34 that is welded or otherwise suitably secured to the walls 24-26 so as to be normal thereto. The end wall portion 34 is substantially flush with the inlet 20 and extends parallel to the axis 20'.

The vertically extending rear wall 26 of the duct A not only functions to define the passage P, but also serves as a splash plate against which sprayback airfuel mixture flowing in the direction of arrow may impinge. The sprayback subsequently is entrained by air passing through the duct toward the carburetor on a succeeding intake cycle of the engine as is indicated by the arrow d. I

The distance I from the carburetor inlet to the wall 26 is an important dimension in achieving proper operation of the inhibiting device. This dimension may vary, within limits, but preferably is 1 inch and is not greater than one and one-half inches. if the rear wall 26 is spaced no more than one and one-half inches from the carburetor inlet, then the fuel-air sprayback mixture returned to the carburetor C in the direction of the arrow d still will be in the vaporized state. Should the distance I be increased to more than one and one-half inches, then the vaporized fuel may not return to the carburetor C, but instead, will fall by gravity to the bottom of the duct, liquify, and collect on the bottom wall 34. If the fuel is permitted to collect at the bottom of the duct, then in time it will flow through the carburetor C and into the combustion chamber 12, thereby stalling the engine.

Although a large amount of the sprayback fuel impinging on the wall 26 will be returned by rebound directly to the opening 20 in the direction of the arrow 11, some of the vaporized fuel, after striking the wall 26, will be deflected or scattered upwardly as shown by the arrow f. The increased area of the passage P,'due to the divergence of the walls 28, will assist in the dissipation of the remaining kinetic energy of the upwardly scattered fuel so that the air drawn through the opening 13 may carry the suspended fuel downwardly in the direction of the arrow g to be returned to the carburetor C. To insure that none of the deflected fuel passes through the inlet opening 32, the inside height of the wall 26 should be at least six inches. With a port 25 having a diameter of one and one-half inches, the distance from the centerline 0 of the port 25 must be at least 5.25 inches from the opening 32. It is important that the end wall 34 be substantially parallel to the path of the sprayback fuel so as to cause a minimum of upward scatter indicated by the arrow f. it is also important that the junction between the bottom wall 34 and the back wall 26 form a right angle so that a minimum of fuel is deflected upwardly.

It also is important that the wall 26 extend substantially normal to the axis of the carburetor air inlet, that the duct be arranged so that its air passage is vertical and its inlet is uppermost so that the force of gravity assists the return of the scattered fuel to the carburetor C. If the duct were arranged so that its inlet is lowermost, the force of gravity would tend to discharge the scattered fuel downwardly through the inlet 32.

Since none of the sprayback fuel moving in the direction of arrow 0 is permitted to pass through the air inlet opening 32, all of the objectionable characteristics of sprayback are eliminated. The fuel which is returned to the engine increases the horsepower output of the engine in addition to minimizing fuel consumption. The engine operates at a cooler temperature and the operation of the apparatus of the two cycle engine is much safer because there is no fuel sprayback to be ignited inadvertently.

It has been found that the sprayback of most two cycle engines is more pronounced at engine speeds below 3,000 r.p.m. Consequently, the amount of fuel returned to the carburetor C is greatest when the engine is operating at low engine speeds. greatest It is to be understood that the drawings and descriptive matter are in all cases to be interpreted as merely illustrative of the principles of the invention, rather than as limiting the same in any way, since it is contemplated that various changes may be made in various elements to achieve like results without departing from the spirit of the invention or the scope of the appended claims.

We claim:

1. In combination:

a two-cycle internal combustion engine having combustion cylinder means providing a piston receiving cylinder wall and a combustion chamber;

a movable piston reciprocable in said cylinder means; and

fuel intake and exhaust ports in said cylinder wall;

a carburetor including inlet means, having an axis and being in communication with said intake port, for supplying said cylinder means with;

vaporized fuel-air mixture during a portion of the engine operating cycle, said engine being operative to blow back a portion of said mixture axially outwardly along said axis through said inlet means during another portion of the engine operating cycle; M

a fuel sprayback inhibitor device mounted on said carburetor comprising duct means including:

a bottom wall generally parallel to said axis and an upstanding wall joined to said bottom wall and being disposed generally above and normal to said bottom wall and said axis, and

means for mounting said duct means on said carburetor with said bottom wall substantially flush with a lower portion of said inlet means.

2. The combination as set forth in claim 1 wherein the distance between said inlet means and said upstanding wall is not more than one and one-half inches.

3. The combination set forth in claim 2 wherein said inhibitor device is vertically disposed.

4. In combination:

a two-cycle internal combustion engine having combustion cylinder means providing a piston receiving cylinder wall and a combustion chamber;

a movable piston reciprocable in said cylinder means, and

fuel intake and exhaust ports in said cylinder wall;

a carburetor, including inlet means, defining an axial passage having an axis, in communication with said intake port for supplying said cylinder means with vaporized fuel-air mixture during a portion of the engine operating cycle;

said engine being operative to blow back a portion of said mixture from said cylinder means axially along said axis through said inlet means during another portion of the engine operating cycle; and

an upwardly opening air intake duct, carried by said carburetor, including axially inner and outer, parallel, walls joined by upwardly diverging side walls to define a vertically extending passageway having an inlet opening at its upper end for admitting air, said inner side wall being adjacent said carburetor inlet means and including an outlet opening at the bottom of said duct registering with said inlet means, a bottom end wall joining said axially inner and outer walls and said diverging side walls and having an interior surface substantially flush with at least a portion of said passage.

5. The combination set forth in claim 4 wherein said outlet opening has an axis aligned with the axis of said inlet means, said end wall being generally parallel to the axis of said outlet opening and said outer wall being generally perpendicular to the axis of said outlet and perpendicular to said end wall.

6. In combination:

a two-cycle, internal combustion engine including:

a combustion cylinder with a piston receiving cylinder wall and a piston reciprocable in said cylinder, said cylinder and piston cooperating to define a variable volume combustion chamber; and

fuel intake and exhaust ports in said cylinder wall,

a carburetor including inlet means, having an axis and being in communication with said intake port, for supplying said cylinder with vaporized fuel-air mixture during a portion of the engine operating cycle, said engine being operative to blow back a portion of said mixture axially outwardly along said axis through said inlet means during another portion of the engine operating cycle;

a fuel sprayback inhibitor device carried by said carburetor comprising:

an upwardly opening duct, including axially inner and outer upstanding walls spanned by bridging wall means, including a lower end wall and opposing side walls which upwardly diverge to form an air passage having an upper opening at its upper end,

said axially inner upstanding wall including an opening in register with said inlet means and being at a level not higher than said upper openmg,

the distance between the carburetor air inlet means and the outer upstanding wall being no greater than one and one-half inches.

7. The combination set forth in claim 6 wherein the cross-sectional area of said upper opening is greater than that of the opening in register with said inlet means.

8. The combination of claim 6 wherein said air passage is substantially free and open to permit the unimpeded flow of air to said inlet means.

9. The combination set forth in claim 6 wherein the spacing between said axially inner and outer walls is one inch. 7

10. The combination set forth in claim 6 wherein said inner wall and said outer wall are parallel to each other and perpendicular to the said lower end wall.

11. The combination set forth in claim 6 wherein said axially outer wall is perpendicular to said axis.

12. The combination set forth in claim 6 wherein the height of said inner and outer walls is not less than 6 inches. 

